Implant device and method for manufacture

ABSTRACT

A knee implant includes a femoral component having first and second femoral component surfaces. The first femoral component surface is for securing to a surgically prepared compartment of a distal end of a femur. The second femoral component surface is configured to replicate the femoral condyle. The knee implant further includes a tibial component having first and second tibial component surfaces. The first tibial component surface is for contacting a proximal surface of the tibia that is substantially uncut subchondral bone. At least a portion of the first tibial component surface is a mirror image of the proximal tibial surface. The second tibial component surface articulates with the second femoral component surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/031,239, filed on Feb. 14, 2008, entitled “Implant Device and Methodfor Manufacture,” which in turn claims the benefit of priority under 35U.S.C. 119(e) to copending U.S. Application No. 60/889,859, filed onFeb. 14, 2007, entitled “Implant Device and Method for Manufacture.”

U.S. application Ser. No. 12/031,239 is also a continuation-in-part ofU.S. application Ser. No. 10/681,749 filed Oct. 7, 2003, entitled“Minimally Invasive Joint Implant with 3-Dimensional Geometry Matchingthe Articular Surfaces”, which in turn claims priority to U.S.Application 60/416,601 filed Oct. 7, 2002, entitled “Minimally InvasiveJoint Implant With 3-Dimensional Geometry Matching the ArticularSurfaces,” and U.S. Application 60/467,686 filed May 2, 2003, entitled“Joint Implants”.

U.S. application Ser. No. 12/031,239 is also a continuation-in-part ofU.S. application Ser. No. 10/997,407 filed Nov. 24, 2004, entitled“Patient Selectable Knee Joint Arthroplasty Devices”; which in turn is acontinuation-in-part of U.S. application Ser. No. 10/752,438 filed Jan.5, 2004, entitled “Patient Selectable Knee Joint Arthroplasty Devices”;which in turn is a continuation-in-part of U.S. application Ser. No.10/724,010 filed Nov. 25, 2003, entitled “Patient Selectable JointArthroplasty Devices and Surgical Tools Facilitating Increased Accuracy,Speed and Simplicity in Performing Total and Partial JointArthroplasty”; which in turn is a continuation-in-part of U.S.application Ser. No. 10/305,652 filed Nov. 27, 2002, entitled “Methodsand Compositions for Articular Repair”; which in turn is acontinuation-in-part of U.S. application Ser. No. 10/160,667 filed May28, 2002, entitled “Methods and Compositions for Articular Resurfacing”;which in turn claims the benefit of U.S. Application No. 60/293,488filed May 25, 2001, entitled “Methods To Improve Cartilage RepairSystems”, U.S. Application No. 60/363,527 filed Mar. 12, 2002, entitled“Novel Devices For Cartilage Repair”, U.S. Application No. 60/380,695filed May 14, 2002, entitled “Methods And Compositions for CartilageRepair”, and U.S. Application No. 60/380,692 filed May 14, 2002,entitled “Methods for Joint Repair”.

The above-mentioned U.S. application Ser. No. 10/997,407 is also acontinuation-in-part of U.S. application Ser. No. 10/681,750 filed Oct.7, 2003, entitled “Minimally Invasive Joint Implant with 3-DimensionalGeometry Matching the Articular Surfaces”.

All of the above patent applications, as well as patent applications andother references mentioned herein below, are hereby incorporated byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates to orthopedic methods, systems and devicesand more particularly, to joint implants and methods for manufacture.

BACKGROUND OF THE INVENTION

Joint implants are well known in the art. For example, one of the mostcommon types of joint prosthetic devices is a knee implant including afemoral component and a tibial component. Other common joint implantsare associated with, for example, the hip and shoulder.

The shape and size of various joint implants are becoming increasinglymore complex and may include, for example, one or more concavitiesand/or convexities, as described in above-mentioned U.S. applicationSer. No. 10/997,407. Traditional implant manufacturing processes, whichmay even include manual steps, and which may be satisfactory for lesscomplex shaping, are becoming inadequate.

Furthermore, joint implants, such as a knee implant that includes tibialand femoral components, often require a relatively large cut on, forexample, the tibia. This is due, in part, to the needed thickness (forstrength and/or reliability) of the polyurethane tibial component. Thecut on the tibia, upon which the tibial component rests, provides spacefor the needed thickness of the polyurethane tibial component, withoutoverstuffing the joint. Such cuts are highly invasive, resulting in lossof bone stock, and over time, osteolysis frequently leads to looseningof the prosthesis. Further, the area where the implant and the bone matedegrades over time, requiring that the prosthesis be replaced. Since thepatient's bone stock is limited, the number of possible replacementsurgeries is also limited for joint arthroplasty.

SUMMARY OF THE INVENTION

One embodiment provides a method for making an implant suitable for ajoint includes providing a blank with a (i.e., at least one) dimensionsmaller than the implant, and material is added to the blank so as toform surface detail on the implant. In related embodiments, addingmaterial to the blank may include laser sintering and/or electron beammelting. Adding material to the block may include adding ceramic(s),metal(s) and/or ceramic-metal composite(s). The material added to theblank may be polished, also. In further embodiments, the blank may bemade of, e.g., polymer(s), metal(s), cross-linked polymer(s),ceramic(s), ceramic-metal composite(s), and/or alloy(s); oruse-appropriate combinations thereof. Providing the blank may includeforming the blank by casting and/or milling. In still furtherembodiments, a three-dimensional shape of a (i.e., at least one, or aportion of at least one) surface of the joint is determined. Determiningthe three-dimensional shape may include the use of imaging, such as MRI,CT, ultrasound, digital tomosynthesis, and/or optical coherencetechniques. The material added to the blank may be, in embodiments, suchthat a surface of the implant is a mirror image of a correspondingsurface of the joint. The implant may be, e.g., a cartilage repair,unicompartmental knee, bicompartmental knee, total knee replacement,hip, shoulder, or interpositional joint implant. An interpositionaljoint implant may be associated with, e.g., a knee, hip or shoulder.

Another embodiment provides a method for making an implant suitable fora joint including providing a blank having a dimension that is differentfrom the implant. The blank is modified using, at least in part, alaser, and/or electron beam melting to form the implant. The formedsurfaces may desirably be polished. In related embodiments, the blankmay include a dimension that is larger than the implant, and whereinmodifying the blank includes cutting the blank with the laser. Laser-cutsurfaces may desirably be polished. In further related embodiments, theblank may include a dimension that is smaller than the implant, andwherein modifying the blank includes adding material by laser sintering.The added material may be desirably polished. The blank may be made ofpolymer(s), metal(s), cross-linked polymer(s), ceramic(s), ceramic-metalcomposite(s), and/or alloy(s); or use-appropriate combinations thereof.The blank may be formed by casting and/or milling. In relatedembodiments, a three-dimensional shape of a (i.e., at least one, or aportion of at least one) surface of the joint may be determined.Determining the three-dimensional shape may include the use of imaging,such as MRI, CT, ultrasound, digital tomosynthesis, and/or opticalcoherence techniques. The blank may be desirably modified such that asurface of the implant is a mirror image of a corresponding surface ofthe joint.

In accordance with another embodiment, a method for making an implantsuitable for a joint includes providing a blank with at least onedimension larger than the implant. A laser, polishing, etching, millingand/or an abrading process is used to cut the blank so as to formsurface detail of the implant. In related embodiments, the blank may bemade of polymer(s), metal(s), cross-linked polymer(s), ceramic(s),ceramic-metal composite(s), and/or alloy(s); or use-appropriatecombinations thereof. Providing the blank may include forming the blankby casting and/or milling.

In still further embodiments, a three-dimensional shape of a (i.e., atleast one, or a portion of at least one) surface of the joint isdetermined. Determining the three-dimensional shape may include the useof imaging, such as MRI, CT, ultrasound, digital tomosynthesis, and/oroptical coherence. The blank may be desirably cut such that a surface ofthe implant is a mirror image of a corresponding surface of the joint.The implant may be, e.g., a cartilage repair, unicompartmental knee,bicompartmental knee, total knee replacement, hip, shoulder, orinterpositional joint implant. An interpositional joint implant may beassociated with, e.g., a knee, hip or shoulder.

In accordance with another embodiment, a knee implant includes a femoralcomponent having first and second femoral component surfaces. The firstfemoral component surface is for securing to a surgically preparedcompartment of a distal end of a femur. The second femoral componentsurface is configured to replicate the femoral condyle. The knee implantfurther includes a tibial component having first and second tibialcomponent surfaces. The first tibial component surface is for contactinga proximal surface of the tibia that is substantially uncut subchondralbone (which may further include overlying articular cartilage.) At leasta portion of the first tibial component surface is a mirror image of acorresponding proximal tibial surface. The second tibial componentsurface articulates with the second femoral component surface. Inrelated embodiments, the second femoral component surface may include atleast one of a ceramic and a metal, and the second tibial componentsurface may include ceramic(s) and/or metal(s). Both the second femoralcomponent surface and the second tibial surface may include metal(s).Both the second femoral component surface and the second tibial surfacemay include ceramic(s).

The second femoral component surface may include one of a ceramic and ametal, and the second tibial surface may include the other of the one ofa ceramic and a metal, e.g., the second femoral component surface may beceramic, and the second tibial surface may be metal. The tibialcomponent may have a thickness of 3 mm or less.

In related embodiments, the tibial component may include an anchoringmechanism, such as a peg and/or a keel. Alternatively, the tibialcomponent may be an interpositional implant that does not include aphysical anchoring mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1 is a flowchart depicting an embodiment of a method formanufacturing a joint implant;

FIG. 2 is a flowchart depicting an embodiment of a method formanufacturing a joint implant; and

FIG. 3 shows an embodiment of a total knee implant, in cross-sectionalview.

DETAILED DESCRIPTION OF THE INVENTION AND EMBODIMENTS

The present invention is directed to methods for making joint implantsthat leverage additive or subtractive manufacturing methods includinglaser sintering and electron beam melting, and to non-invasive jointimplants which may be advantageously made by the methods describedherein. Such implants may feature a surface of the implant that isadvantageously a mirror image of the joint surface. In anotherembodiment, non-invasive joint implants that rest on substantially uncutsubchondral bone are described. The invention is now described infurther detail, below.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a device” includes aplurality of such devices and equivalents thereof known to those skilledin the art, and so forth. Similarly, the terms “a” (or “an”), “one ormore” and “at least one” can be used interchangeably herein. Also, theterms “comprising”, “including”, and “having” can be usedinterchangeably.

It is to be understood that the implants described herein may beassociated with a wide variety of joints, including, without limitation,joint implants used in a knee, shoulder, hip, vertebrae, elbow, ankle,hand, foot and wrist.

FIG. 1 is a flowchart depicting a method for manufacturing a jointimplant, in accordance with one embodiment of the invention. In step101, a blank is provided with at least one dimension that is larger thanthat of the (final) implant. The dimension of the implant may be, e.g.,a partial or uniform thickness, length, width, or curvature. The blankmay be made, without limitation, a polymer, a metal, a cross-linkedpolymer, a ceramic, a ceramic-metal composite, and/or an alloy.

Suitable materials for use in joint implants and methods describedherein can include metals and metal alloys including CoCrMo, CoCr,titanium alloys and commercially pure TI (cpTi), medical grade stainlesssteels, tantalum and tantalum alloys, and Nitinol (“NiTi”). Particularlyadvantageous materials are those well-suited, or specifically designed,for laser sintering or electron-beam melting manufacturing techniques,e.g., ASTM F-75 CoCr alloy, or Arcam Ti6Al4V ELI titanium alloy(available from Stratasys, Eden Prairie, Minn.) Ceramic materials, e.g.,aluminum oxide or alumina, zirconium oxide or zirconia, compact ofparticulate diamond, and/or pyrolytic carbon may be used.

In various embodiments, the blank is dimensioned to be, in one or moreportions, only slightly larger than that of the implant. For example,the blank may be milled or cast such that all, or certain portions ofthe blank, are only slightly larger than the implant. Providing a blankfrom which material will be removed to arrive at the precise implantsize, geometry and surface characteristics, simplifies manufacturingprocessing and is believed to ensure reproducibility. The blank may beprovided, e.g., by casting, milling, forging, compression molding,extruding or injection molding.

In various embodiments, a library of blanks may be kept of varying sizeand shapes. Upon determining an implant size, an appropriately sizedblank may then be chosen.

Upon providing the blank, the blank is cut with a laser so as to formsurface detail of the implant, step 105. Separately, or in addition tolaser cutting, the blank may also be cut using precision milling orgrinding, or other abrading processes known in the art. For example,after cutting the blank with the laser, the surface of the blank maydesirably be polished.

In various embodiments, the method may further include determining athree-dimensional shape of at least one surface of the joint, step 103.Using the three-dimensional shape, the blank may be cut in step 105 suchthat a surface of the implant, or a portion thereof, is a mirror imageof the corresponding joint surface (or portion thereof). For example,the implant surface may comprise a surface that is a mirror image of thejoint surface to which the implant surface is designed to mate, so thatthe implant surface conforms to the joint surface, ensuring that thedevice fits the joint surface in precisely the correct location. Theimplant surface may alternately comprise more than one such mirror imagesurfaces, e.g., to assist in placement in the device, i.e., the implantsurface need not comprise one contiguous mirror image of the jointsurface. A series or pattern of smaller implant mirror image surfaces,each corresponding to or matching an area of the joint surface, can beprovided. Without limitation, one application of this would be toprovide grooves in which cement for affixing the device may be applied,so the device may be attached to the joint surface without flowing ontoother areas of the implant surface. Another non-limiting applicationwould be where a continuous conforming surface were not necessary, e.g.,where the device may be properly seated by matching two, three, four ormore conforming “reference surfaces” to corresponding areas of the jointsurface. The area of the mirror image surface desirably should besufficient to ensure that the device is located properly. Where thereare more than one of these “reference surfaces”, the area of each shouldbe use- and application-appropriate, but a range of 1, 2, 3, 4, 5 cm² ormore for each reference surface is contemplated. Where there is oneimplant surface with a mirror image, smaller areas comprising a mirrorimage are possible, as well as the entire implant surface. The jointsurface may include at least one concavity and/or convexity.

Using the approach generally outlined in FIG. 1., a non-invasive jointimplant, such as those described in above-mentioned U.S. applicationSer. No. 10/997,407, may be manufactured. The implant may be, forexample, a cartilage repair implant, a unicompartmental knee implant, abicompartmental knee implant, a total knee replacement implant, a hipimplant, and a shoulder implant. The implant may also be aninterpositional implant, such as the implant described inabove-mentioned U.S. Application No. 60/784,255.

Determining the three-dimensional shape of the joint surface may includea wide variety of imaging methodologies. For example, the imaging mayinclude MRI, CT, ultrasound, digital tomosynthesis, and/or opticalcoherence. Reference is made to the above-mentioned U.S. applicationSer. Nos. 10/997,407 and 10/728,731 for how imaging technologies areused to derive the three-dimensional shape of the joint surface. The 3-Dinformation is then used in the CAD/CAM system to form the implantshape, geometry, and surfaces to make the desired implant.

FIG. 2 is a flowchart depicting a method for manufacturing a jointimplant, in accordance with another embodiment. In step 201, a blank isprovided with at least one dimension that is smaller than that of the(final) implant, instead of larger as described in FIG. 1. Material isthen added to the block to form surface detail on the implant (step205.)

The material may be added to the block using additive manufacturingtechnologies including laser sintering and/or electron beam melting. Inlaser sintering, a high power laser, such as a carbon dioxide laser, isused to fuse small particles of plastic, metal, or ceramic powders intoa mass representing a desired three-dimensional object. Generally, thelaser selectively fuses powdered material by scanning cross-sectionsgenerated from a 3-D digital description of the part (e.g., from a CADfile or scan data) on the surface of a powder bed. After eachcross-section is scanned, the powder bed is lowered by one layerthickness, a new layer of material is applied on top, and the process isrepeated until the part is completed. Laser sintering can produce partsfrom a relatively wide range of commercially available powder materials,including polymers, ceramics, and metals (such as steel, titanium,alloys and composites)

Full melting, partial melting, or liquid-phase sintering may be used.Electron beam melting involves melting or fusing metal, ceramic or othervarious powders, so as to build the part layer by layer. Exemplaryelectron beam melting systems are available from Stratasys, EdenPrairie, Minn.

After adding material to the blank, the surface of the blank may bedesirably polished. Furthermore, and similar to above-describedembodiments, the method may further include determining athree-dimensional shape of at least one surface of the joint, step 203.Using the three-dimensional shape, material may be added to the blank instep 205 such that at least one surface of the implant is a mirror imageof at least one surface of the joint. The implant may be, for example, acartilage repair implant, a unicompartmental knee implant, abicompartmental knee implant, a total knee replacement implant, a hipimplant, and a shoulder implant. The implant may also be aninterpositional implant, such as the implant described inabove-mentioned U.S. Application No. 60/784,255.

Determining the three-dimensional shape of the joint surface may includea wide variety of imaging methodologies. For example, the imaging mayinclude MRI, CT, ultrasound, digital tomosynthesis, and/or opticalcoherence. Reference is made to the above-mentioned U.S. applicationSer. Nos. 10/997,407 and 10/728,731 for how imaging technologies areused to derive the three-dimensional shape of the joint surface. The 3-Dinformation is then used in the CAD/CAM system to form the implantshape, geometry, and surfaces to make the desired implant.

In accordance with another embodiment, a joint implant is presentedwherein at least one surface of the implant rests on subchondral bone,and advantageously does not require invasive cutting of bone. Theseimplants may be advantageously made by the methods describedhereinabove. While an exemplary knee implant is described, it is to beunderstood that the joint implant may be associated with, for example, ashoulder, a hip, a vertebrae, an elbow, an ankle, a hand, a foot or awrist.

FIG. 3 shows in cross-section a total knee implant, in accordance withone embodiment. A femoral component 301 includes a first femoralcomponent surface 303 for securing to a surgically prepared compartmentof a distal end of a femur 305. A second femoral component surface 307replicates the shape of the femoral condyle(s).

A tibial component 311 includes a first tibial component surface 313 forresting on and contacting a proximal surface of the tibia. The proximalsurface of the tibia may advantageously include substantially uncutsubchondral bone. In illustrative embodiments, at least a portion of thefirst tibial component surface 313 is a mirror image of the proximalsurface. For example, a three-dimensional image of the proximal surfacemay be obtained as described above, with the first tibial componentsurface 313 manufactured based on the three-dimensional image. A secondtibial component surface 317 articulates with the second femoralcomponent surface 307. It is to be understood that in a total knee jointimplant, the tibial component(s) cover both the medial and lateralplateau. In various embodiments, the tibial component may be a singlecomponent that covers both the medial and lateral plateau (and may ormay not leave the tibial spines intact), or may include two components(i.e., a tibial component for the medial side and a tibial component forthe lateral side). In other embodiments, for example, a unicondylar kneeimplant, the tibial component may cover either only the medial orlateral plateau.

In an exemplary embodiment, the femoral component 301 and the tibialcomponent 311 may each be approximately 2-3 mm thick. The thickness maybe, for example, similar to the thickness of cartilage removed inpreparing the joint for implantation. Thus, overstuffing of the joint isminimized while providing a non-invasive alternative to traditionalinvasive knee surgery. Heretofore, such implants having the requisitedimensions and strength were not easily achievable. Some or all of thecartilage on the femoral and/or tibial articular surfaces may be removedto prepare the joint for receiving an implant (i.e., to expose some orall of the subchondral bone) as necessary, depending on the progressionof cartilage wear, disease, etc. The interior surfaces of the femoraland/or tibial component may be accordingly designed so the implant maybe affixed directly to the desired exposed area(s) of subchondral bone.The thickness and/or shape of the femoral and/or tibial components maybe determined (e.g., so as to reconstruct the thickness of theoriginally present articular cartilage) from an image-derivedsubchondral bone shape of the joint surfaces, as described in theabove-mentioned U.S. application Ser. No. 10/305,652.

To provide the required strength (e.g., for biomechanical loading) andreliability, and still be thin enough to avoid overstuffing the joint,the first tibial surface 313 and/or the second tibial surface 317includes, without limitation, a metal and/or a ceramic. For example, thesecond femoral component surface 307 may includes at least one of aceramic and a metal, and the second tibial component surface 317includes at least one of a ceramic and a metal. In another example, boththe second femoral component surface 307 and the second tibial surface317 include a metal. In still another example, both the second femoralcomponent surface 307 and the second tibial surface 317 include aceramic. In yet another example, the second femoral component surface307 includes one of a ceramic and a metal, and the second tibial surface317 includes the other of the one of a ceramic and a metal.

In various embodiments, the knee implant includes an anchoring mechanism330. The anchoring mechanism 330 may be, without limitation, a peg and akeel protruding from the first tibial surface 313.

The foregoing description of embodiments of the present invention hasbeen provided for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseforms disclosed. Many modifications and variations will be apparent tothe practitioner skilled in the art. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application, thereby enabling others skilled in the art tounderstand the invention and the various embodiments and with variousmodifications that are suited to the particular use contemplated.

What is claimed is:
 1. A method of manufacturing an implant forrepairing a knee joint of a patient, the method comprising: a. derivinga three-dimensional shape of the knee joint of the patient from imagedata of the knee joint of the patient, wherein the image data includeinformation about a shape, geometry or articular surface of a femoralcondyle of the knee joint of the patient, b. providing a blank with atleast one dimension larger than a corresponding dimension of the femoralcondyle of the knee joint of the patient; and c. altering the blank toobtain a desired shape of the implant, wherein the desired shapereplicates the femoral condyle of the knee joint of the patient in thecorresponding dimension.
 2. The method of claim 1, wherein the implantincludes a medial condylar portion and a lateral condylar portion. 3.The method of claim 2, wherein the implant further includes a tibialcomponent that provides both medial and lateral tibial plateaus.
 4. Themethod of claim 3, including configuring the tibial component to leavetibial spines of the knee joint of the patient intact.
 5. The method ofclaim 3, including configuring the tibial component not to leave tibialspines of the knee joint of the patient intact.
 6. The method of claim2, wherein the tibial component includes a first portion that providesthe medial tibial plateau and a second portion that provides the lateraltibial plateau, wherein the first and second portions are separatelyformed.
 7. The method of claim 1, including entering thethree-dimensional shape into a CAD/CAM system.
 8. The method of claim 7,wherein the CAD/CAM system is used to form the desired shape of theimplant.